1. Field of the Invention
This invention relates to exposure indicators in single lens reflex cameras.
2. Description of the Prior Art
It has been known from the art to provide an arrangement of lamps or light emitting diodes (hereinafter referred to as LEDs) for visually indicating exposure values, such as the setting of the diaphragm or the exposure time in the view-finder of a photographic camera. In the case of single lens reflex cameras whose light metering aspect is of the so-called "TTL" type, since it is required that the photo-sensitive element in the finder optical system be exposed to only light entering through the objective lens to avoid any reduction of the accuracy of exposure control, the incorporation of such an LED arrangement into a space adjacent the finder optical system has not been undertaken until a solution has recently been proposed in U.S. Pat. No. 4,035,815. According to this proposal, the actuation of the LED is controlled to light up after the photo-sensitive element is no longer effective to derive the exposure value.
In application of such exposure indicator control circuit to a single lens reflex camera having a digital exposure value computer almost always associated with a repeatedly operated light metering system, it is, however, difficult to enhance the intensity of light from the energized LED, because the period of actuation of each LED is limited to a very short value defined as between the transition from the first to the second half of each cycle of light metering operation and the start of the following cycle. Consequently, when the scene light is very bright, the rapid reading of the exposure indicium becomes almost impossible to achieve, and, therefore, the photographer is unable to determine whether one or more of the adjustable exposure factors are correctly set.